Ben 10: Ultimate Justice
by Karma826
Summary: The Team gets a new member: Ben Tennyson from another universe! What will happen to him and the team? Please R&R.
1. An Alien Falls Out of the Sky(Literally)

**Disclaimer: I do not own Ben 10 or Young Justice.**

**Ben 10: Ultimate Justice**

**-June 21, 2011-Original Ben 10 Universe-**

Ben Tennyson sat on the last remaining skyscraper in Bellwood, think about what had just happened. Everything had gone by so fast, and Ben hadn't been able to anything.

A giant warship had appeared over Earth, and destroyed ever single human being on Earth with a blue laser. No one had been spared-except for Ben.

The only reason he was alive was because of the Ultimatrix. He was able to activate it and save himself, only to watch his family and friends be destroyed.

Now Ben was crying, because he knew this was the end of the world. He knew that only he survived the attack, and that nothing could bring back the human race.

He looked down at the ground 500 meters below. Then he made his decision, for there was no purpose left in the galaxy for him. He stood up, wiped his tears with his left arm, and jumped.

He flew straight down at the ground, going faster and faster. Then the Ultimatrix flashed and said "Galactic scan completed. Human race detected." Ben's eyes widened and before he knew he activated the Ultimatrix and slammed down on it. There was a green flash and immediately a blue flash right behind it.

**-June 21, 2011-Young Justice Universe-**

The team was in the mission briefing room which was now converted to be a training room. Superboy and Aqualad were sparing and of course Superboy had the upper hand. He slammed his fist into Aqualad's shield created from his Water-Bearers and Aqualad stepped backwards.

Suddenly, there was a blue flash at the ceiling and a vine like creature fell out. The entire team stopped whatever they were doing and stared at the strange creature. The creature then stood up and shouted "**SWAMPFIRE**!"

The alien had root like feet, mostly green with black on it sides, red spikes on its shoulders, red and yellow spikes on its head, green eyes, and a black and green hourglass symbol on its chest.

_What is that thing_? KD asked through the telepathy link. _I do not know..._ Aqualad answered. Swampfire looked around and looked surprised. "Where am I?" he asked. "Wait... There's no more humans on Earth, so you must all be impostors!"

Swampfire ignited the methane in his palms and two fireballs appeared.

Kid Flash yelled, "RUN!"

Everyone scrambled for nonexistent cover as Swampfire threw barrage after barrage of fireballs at the team.

"Hold still, you alien scum." Swampfire growled as he missed everyone.

Kid Flash ran circles around Swampfire, who was in the middle of the room.

"Nah nah you can't catch me." KD taunted right as Swampfire threw a well placed shot that threw Kid Flash against the wall and he crumbled to the ground, unconscious.

"You will pay for that" Aqualad growled as he and Superboy charged Swampfire.

Aqualad took out his Water-Bearers and made them into swords. Superboy, who was faster, charged Swampfire and punched him-only to find his fist go right through Swampfire's stomach.

Swampfire grinned and said, "My turn."

Swampfire kneed Superboy's chin, which caused Superboy's head to snap upwards. Then Swampfire pulled Superboy's fist out of his stomach, threw him up, and punched him into the side of the room.

Aqualad took advantage of the distraction and cut off both of Swampfires' arms and was startled at this. The entire team also froze and stared at the two arms on the ground.

Swampfire turned around, chuckling. "You realize that won't help you at all." he said as two light green vines came out of the stubs of his arms and reattached the arms on the ground to Swampfire's body.

Swampfire then punched at Aqualad, who ducked instinctively and swung his swords at the Methanosian.

Swampfire threw up his arms to block the attack, but the swords cut right through them.

The arms re-grew instantly and Swampfire light his hands on fire and fired a column of fire at Aqualad.

Aqualad quickly morphed his swords into a shield, but the fire was getting uncomfortable for the Atlantean.

The rest of the team was busy helping KD and Superboy recover when Robin saw Aqualad was in trouble.

Robin ran toward the large vine creature and threw an explosive Batarang.

It lodged in Swampfire's stomach and detonated.

When the smoke cleared, the entire team saw that only the legs and lower torso remained of the vine like creature.

Suddenly, the vines started growing again and within seconds, Swampfire was normal again.

The team could only watched stunned as it said, "My turn." and smashed Aqualad into the far wall. Then it let loose a column of fire at the rest of the team.

Rocket, Zatana, and M'gann put up a shield to stop the fire but the heat was too much M'gann and she passed out.

"M'gann!" Artemis yelled, as she rushed over to her.

Robin jumped around the shield and charged Swampfire. Swampfire saw him and ceased firing and grabbed 3 spikes off his shoulders, which re-grew immediately.

He then threw the spikes at Robin, which then sprouted vines and grabbed Robin, keeping him occupied while Swampfire returned his attention to Rocket and Zantana, who were charging him.

They both threw discs of energy at him, but they simply went right through him or cut his arms or legs, which instantly re-grew. Swampfire then threw some fireballs at the two girls but they created shields to block it.

Swampfire said, "It seems we're at a standoff girls... OR NOT!"

He then hit the Ultimatrix symbol on his chest and four spikes popped out of it. Then the transformation began, and when it was finished, the result dumbfounded the girls and Robin.

"**ULTIMATE SWAMPFIRE**!" He bellowed out at everyone.

Ultimate Swampfire then proceeded to grab seeds off his back and throw them at the two girls in front of him.

The vines instantly captured Zantana but Rocket reacted faster and created a sphere shield around her. The vines attempted to break the shield, but to know avail.

Ultimate Swampfire then fired bombs at the shield, but the shield still didn't break.

Rocket then yelled to the creature, "You can't break this shield. It's powered by kinetic energy, so all the smashing and bashing will just power this shield forever!"

"Oh really" Ultimate Swampfire muttered when suddenly two batarangs sliced through his arms.

"Hey!" Ultimate Swampfire yelled in surprise. But before he could do anything, a small device landed in front of his feet and froze him.

"Ugh. I thought I would never get free of those vines." Robin said.

Ultimate Swampfire eyes widened as he saw that all the vines that were holding Robin had been disintegrated.

"Luckily I still had some acid to disintegrate the vines" Robin said with a smug smile. He walked up to the frozen Methanosian and said, "So what does it feel like being powerless now hmmm?"

Ben could only stare at the Boy Wonder in shock, trying to comprehend how this boy had defeated Ultimate Swampfire.


	2. Alternate Reality

**Disclaimer: I do not own Ben 10 or Young Justice but i own this awesome plot! (I think...)**

**AN: This book was inspired by Sandman7734 and that's why Ben is crying in the beginning. Don't worry, there won't be anymore of Ben crying. Also, only one or two omniverse aliens will be in here. Oh and Ben doesn't have a timer. The Ultimatrix only times out when Ben wants it too or when he's unconscious. But Ben still needs to touch the Ultimatrix symbol to transform.**

* * *

Chapter 2: Alternate Reality

Ben watched as the masked boy touched something in his ear and starting talking. Then the boy, Robin, he thought, walked over to his comrades to help them up.

All the while, Ben was waiting for the right moment to execute his plan. He had already been in this predicament once before. All Ben had to do was to heat up the temperature in his body, melt the ice, re-attach his arms, and get the hell out of there.

Right when Ben was about to start melting the ice, a bright light appeared inside the tubes at the other end of the cave and people starting walking out of them.

_Teleportation device_ Ben thought in his head.

Now was the to get out, while everyone was distracted. Ben increased his body temperature fast enough to turn the ice directly to steam.

The guy dressed in black with a cowl reacted faster than Ben thought and threw a boomerang at Ben.

Ben rolled out of the way and re-attached his arms. He then threw down some smoke bombs and turned toward the wall.

He then let loose a huge wave of intense fire that burned a hole through solid rock. As Ben climbed through the hole a golden lasso caught him around the waist and prevented him from moving any farther.

"Going somewhere?" a female voice said. Ben turned around and saw one of the most beautiful women he had ever seen-besides Julie, of course.

"Yeah, I was just leaving." Ben replied.

"Well you're not going anywhere until we have answers." The man the cowl and black clothing said.

"Well that sucks for you because I'm just gonna leave and there's nothing you can do to stop me." Ben said and then pulled the lasso off him.

"I don't think so" The guy in blue tights with a S symbol on his chest said.

Ben turned and said, "And how are you going to stop me?"

"By doing this" the man replied and red lasers came out of his eyes and hit Ben in the chest, knocking him back onto the beach outside.

Ben groaned and got up only to see that he was surrounded by the man with the cowl, the "S" guy, the woman with the lasso, another guy with a lightning bolt on his chest, a green guy who looked like a Martian, another guy dressed in green who had a weird symbol on his chest, and a guy who had scales on his chest.

"Surrender now, and we won't hurt you. This is your only warning." The guy in black who had a bat symbol on his chest said.

"I don't think so" Ben growled and touched the Ultimatrix symbol on his chest.

"**HUMUNGOUSAUR**!" Ben yelled in a deep voice after his transformation.

"What in the world?" The guy clad in red with the lightning bolt said in surprise. The rest of the people present seemed to have similar reactions.

Ben smiled and started to grow to full size. The heroes were still too shocked to do anything until it was too late.

Humungousaur slammed his fist into the ground causing a mini earthquake and knocking everyone to the ground. Then as everyone started to get up, Ben hit the Ultimatrix again and seemed to vanish into thin air.

"Where did he just go?" Flash asked but nobody had an answer to give.

* * *

**-Somewhere in Happy Harbor-**

Ben had found an empty street in the town that was apparently called "Happy Harbor" and changed back from Nanomech to regular Ben. He had used this alien to escape the costumed people because he wasn't sure that he could take them all on. Now he stood on the deserted street, wondering where the heck he was.

He had never heard of a town named Happy Harbor, and he had a sneaking suspicion that this was not his Earth, but some alternate reality. To confirm this, he held up his left wrist and played around on the Ultimatrix, until he activated the communications function.

"Ummm hello? Gwen? Kevin? Grandpa Max? Anybody there?" Ben said into the device while walking down the street.

Suddenly there was a reply, but not one Ben was expecting.

"Hello? Which Green Lantern is talking rubbish on a secure line? Please state your name and sector." an alien voice said.

Ben blinked I'm surprise. This confirmed his suspicions-the famous Ben 10 was in another universe, without a way to get home.

"Hello? Please respond, Green Lantern, or else I will have to report this misuse of the secure Green Lantern communications line." The alien said again.

Ben just sighed and shut off the communications. His thoughts then turned to one name: Professor Paradox. The person who was one with the time stream-the only person who could send him to alternate realities.

Then his mind wandered back to the current situation-and Ben realized he would have to find a place to stay while waiting for Paradox to come and find him. That wasn't a problem though, he could just use Diamondhead and sell the crystals that Diamondhead could produce.

Right when Ben was about to do that he remembered that he was in an alternate reality and that he should first go search up on the Internet about any heroes in this world.

* * *

**-5 minutes later-**

Ben was sitting in the Internet cafe with a cup of coffee surfing the Internet. Apparently there was a Justice League in this world which kept peace and protected the Earth from extraterrestrial attacks. But there was no mention of the teen heroes, who looked like miniature replicas of some Justice League heroes.

Ben sighed and logged off the computer and paid for the coffee and Internet connection. He then walked out of the cafe, onto a deserted street and activated the Ultimatrix. After selecting the correct form, Ben slammed down on the core and proclaimed: "**XLR8**!"

Then with his abilities of manipulating friction XLR8 took off at 500 miles per hour toward Washington D.C., where the Justice League headquarters were located. Little did he know that the real headquarters were in space, orbiting Earth.

-Inside the Cave-

"I just detected a large energy signal headed toward Washington D.C. at super fast speeds. It's the same exact energy signature that was emanating from that Swampfire creature." Batman said while tapping away at a holographic keyboard.

"Flash, I need you and Kid Flash-if he can, of course- to go check it out. The rest of the team and league will meet you up wherever the energy signal goes."

"Got it Bats. Come on kid, I'll race yea." Barry Allen AKA The Flash said to Wally as they speed out of the cave."

-Hall of Justice, 30 minutes later-

XLR8 stopped in front of the Hall of Justice and looked at the grand building. He opened his visor and said, "Well, these superheroes seem to have a large budget." With that said, Ben closed his visor and raced inside.

A few people inside who were looking around turned and stared at the blue creature who had seemed to appear out of thin air. They all looked curiously at this alien, thinking him a superhero but not remembering where they saw the creature.

A reporter, Cat Grant, who was at the Hall of Justice waiting for an interview with Icon, saw this mysterious blue creature and decided to investigate.

She walked over to Ben and asked, "Who are you, and are you a new superhero in the Justice League?"

Ben turned around and was used to people interviewing him, but wasn't used to people asking who he was.

Ben decided to go cool, macho superhero style guy and said, "Who am I? I'm XLR8, one of the newest heroes to this world. And no, I'm not in the Justice League, actually, I never heard about the Justice League until today."

Grant was surprised at this information and stored it mentally in her head-this might be an interesting story. Suddenly The Flash and Kid Flash appeared right behind XLR8 while the doors to the inner parts of the Hall of Justice opened revealing Batman, Superman, Green Lantern, and Wonder Woman.

"Oh... Gotta go bye!" XLR8 quickly said and put down his visor and was gone in a blur out the doors.

"Stop him!" Batman yelled as Flash, Kid Flash, and Superman used their speed to catch up with the alien. Green Lantern quickly created a platform for Batman to stand on and flew after the speedsters. Wonder Woman also followed in pursuit.

Grant blinked in surprise-the "hero" she just talked to was apparently a fugitive of the Justice League!

* * *

**AN: Thanks for reading! The review really kept me motivated. Also, give me ideas for future chapters!**


	3. Humiliation

**AN: Sorry for the long wait. I had a lot of stuff to do and had no time to write. But here's the third chapter! Enjoy! Also, I have a poll on my profile for a new Ulitmate alien. Chose the alien, and give me some idea for new powers :D**

**Disclaimer: I do not own Ben 10 or Young Justice.**

* * *

Chapter 3: Humiliation

Ben was running as fast as he could when The Flash and Kid Flash caught up with him easily at 500 miles per hour right as they crossed into New York City. Ben saw the two speedsters and decided to take care of them and raced into an alley way right next to him. He then stopped and turned around.

The Flash stopped with Kid Flash right behind him and said "Halt! You are under arrest for attacking the Justice League and the Team."

"Anything else?" XLR8 asked, "Cause I'm outta here."

With that said he hit the Ultimatrix on his chest and transformed with the usual green light.

**"DIAMONDHEAD!"**

For some reason this transformation still shocked the two speedsters and Ben took advantage of this distraction. He shot a round of diamond shards at them and they reacted and sidestepped the deadly shards.

Suddenly, diamonds grew around them and encased them in a shell. The Flash easily vibrated out of them but Kid Flash couldn't do that without exploding the crystal.

The Flash looked at Wally for a second to make sure he was okay and Diamondhead took advantage of the distraction and punched Barry Allen into the wall.

The famous Flash smashed into the wall and fell unconscious as Kid Flash watched in horror. Ben then created diamond platforms and jumped up to the rooftop when a laser beam hit him in the chest into the middle of Time Square.

A bunch of pedestrians gathered around Ben as he got up, taking pictures and video, when a green cage surrounded Diamondhead.

"Attention! You are under arrest for attacking the Justice League and the Team, as well as half destroying Mount Justice!" Green Lantern Hal Jordan said, his voice booming across Time Square, as six of the seven original Justice League members landed in a circle around Ben.

"Is that all?" Ben asked sarcastically, "Cause this is getting old."

He then tapped the Ultimatrix again and when the green light died down, there was nothing in the cage.

"Where did he go?" Superman asked as everyone looked around for the shape-shifting creature.

"He's gone, but I'll have the team track the thing down and bring it back for interrogation." Batman replied.

* * *

**-The Cave, the next day-**

"Team, your mission is to track down the shape-shifting creature, designated 'Transformer'." Batman said. "You are to leave immediately in the bioship and track down the energy signature whenever it appears. Also, to begin your search start at the last know location of the signature, which is in NYC. Dismissed."

"Alright, payback time!" Wally said as the team walked to the hanger and boarded the bioship.

* * *

**-New York City, the same time-**

Ben yawned as he walked out of the cheap motel he had slept in for the night. He would have already created diamonds with Diamondhead last night but he was too lazy and he didn't want to attract anymore attention to himself.

_Time to become rich._ Ben smiled as he walked into an empty alleyway and activated the Ultimatrix.

**"DIAMONDHEAD!"**

He then proceeded to shot several rounds of diamonds into the ground. After this he pulled the diamonds out of the ground and transformed back into Ben.

Ben put the diamonds into his jacket and pant pockets and walked out of the alley humming, looking for a jewelry store.

* * *

**-On the bioship-**

"Scanners just picked up the energy signature briefly in Lower Manhattan." M'gann said from her pilot seat.

"Did you get a specific location?" Robin asked.

"Negative. The energy signature was too powerful for the scanners." M'gann replied.

"Alright, take us to Lower Manhattan. We'll start our search there." Robin said.

* * *

**-1 Hour Later-**

Ben walked out of the fifth jewelry store he had visited with his pockets full of cash and devoid of diamonds.

_I have 10000 dollars in my pockets right now, probably a good idea to find a place for the night and a laptop._ Ben was thinking when he saw Robin jump from a rooftop.

_Oh great, now those teenage sidekicks are after me._ Ben thought as he rushed into an appliances store that sold high quality laptops, according to the sign plastered across the window.

Ben quickly scanned the aisles and found the best laptop the store had. Even though the price was very high, money wasn't a problem now for Ben Tennyson.

He quickly paid for the laptop, and hurried out of the store only to be nearly knocked down by a yellow blur.

"Woah! Sorry dude!" Kid Flash said as ran off again.

_Hmmmm they don't seem that bad._ Ben thought as he walked toward a 5 star hotel.

* * *

**-2 hours later-**

_Team, status report._ Robin said into the telepathic link.

_Nothing still._ Superboy replied.

_I'm hungry._ KF said.

_A no for me and idiot here._ Artemis also said.

_Everyone else?_ Robin asked.

_No, sorry Robin._ Everyone else replied at the same time.

_Alright, we'll take a break on the bioship._ Robin said again.

_Jeez, you'd think a shape shifting alien thing would be easier to find._ Wally said as he raced back to the bioship, hungry for snacks.

* * *

**-At the same time, in a five star hotel-**

Ben got out of the shower and changed into some pajamas he had bought in the hotel with some money.

"Ahhhh, this is the life." Ben said to himself as he collapsed on his bed.

"Well, time to get to work. First, I think I'm going to need an identity in this universe."

He opened up his laptop and turned it on. Then he activated the Ultimatrix and selected Upgrade.

**"UPGRADE!"**

Ben then morphed with the laptop and hacked into several government databases and created himself an identity. He then shipped a hard copy of the identification to his room in the hotel. After this he created himself a bank account and unattached himself from the laptop.

"Time to cash in a huge deposit." Ben said as he transformed into XLR8 and raced to the nearest bank.

* * *

**-At the same time on the bioship-**

_Beep beep beep_

"Everyone up!" Robin yelled. "The energy signature has been activated! Everyone get out there and looking for the 'Transformer'!"

* * *

**-In front of a bank-**

Ben stopped in front of the 24 hour bank and transformed back to human. He then walked in and deposited all of his cash money.

As he was walking out the teenage heroes dropped down in front of him and raced toward him.

"Hey you!" Robin yelled at Ben.

"Yes?" Ben asked warily, thinking that might have figured out who he was.

"Have you seen an shape shifting alien around here?" Robin asked.

"Nope. I think I would have noticed." Ben replied with relief.

"Ok, thanks." Robin said as the team spread out, obviously looking for Ben.

Ben nodded and walked away whistling, thinking how close of a call that was.

* * *

**-2 days later-**

Ben was lounging in his penthouse, thinking about the last two days. So much had happened, in so little time.

After the encounter at the bank, Ben had waited for his copy of identification and then used Graymatter to create himself a fortune by investing in the stock market. After this, Ben had bought a penthouse and bought the parts needed to create alien technology.

The first thing he made was an energy disrupter that spread out the Ultiamtrix's energy signature across the city so the Justice League never had an exact location. The next thing he did was upgrade the penthouse with alien tech and an advanced AI that scanned the news for danger in the city.

Right when Ben was about to fall asleep, the AI turned on the TV, showing a scene of a robot that was fighting the teen heroes in Time Square. The bad thing though, was that the super heroes were losing and Ben knew what he had to do-hero time.

* * *

**NEXT CHAPTER: AMAZON, PART 1**


End file.
